**4. Experimental Results**

A three-module, proof-of-concept prototype was built and tested to verify the operation of the MCSI. Unlike previous MCSI prototypes, having custom-designed inductors that are strictly identical was not required for proper operation of the converter [11]. In fact, the inductors used in the prototype are off-the-shelf 20 mH inductors with ± 5% tolerance [18]. The unidirectional switches used in the modules are realized by connecting a SiC diode in series with an IGBT. The modified LS-SPWM, CBA, and data acquisition were implemented in a dSPACE MicroLabBox. All the measured voltages and currents were sent to dSPACE ControlDesk and then plotted using Matlab. Figure 8 shows a picture of the experimental setup. The rest of the prototype's parameters are given in Table 2.

**Figure 8.** Experimental setup.

**Table 2.** Prototype parameters.


Initially, only two modules were used to create a five-level MCSI. The operation of the five-level MCSI during startup is shown in Figure 9. The CBA's effectiveness is apparent in Figure 9b,c; the instantaneous values of the sharing inductors' currents remained close to each other during startup. Figure 10 shows the same quantities under steady-state conditions. The CBA's efforts can be observed in Figure 10b,c. When the output current of any phase is at its positive peak, referred to as odd intervals in Section 3, the upper sharing inductors experience similar *di*/*dt*, because they are connected to the same phase. On the other hand, the lower sharing inductors' currents are changing at various rates, which shows the CBA's effort to balance the inductors' currents. When the output current of any phase is at its negative peak, the same phenomenon is reversed, changes are more apparent in the upper inductor's currents.

**Figure 9.** Operation of the five-level MCSI during startup: (**a**) output current, (**b**) upper inductors' currents, (**c**) lower inductors' currents and (**d**) output voltage.

**Figure 10.** Steady-state operation of the five-level MCSI: (**a**) output current, (**b**) upper inductors' currents, (**c**) lower inductors' currents and (**d**) output voltage.

For further testing and verification, the third module of the prototype was activated to enable a seven-level operation. All the key waveforms of the seven-level MCSI during startup and steady-state operating conditions are presented in Figures 11 and 12, respectively. Further demonstration of the effectiveness of the CBA is shown in Figure 12b,c.

**Figure 11.** Operation of the seven-level MCSI during startup: (**a**) output current, (**b**) upper inductors' currents, (**c**) lower inductors' currents, and (**d**) output voltage.

**Figure 12.** Steady-state operation of the seven-level MCSI: (**a**) output current, (**b**) upper inductors' currents, (**c**) lower inductors' currents and (**d**) output voltage.
